Power Management Of Blasting Lead-In System

ABSTRACT

A blasting system ( 10 ) in which detonators ( 12 ) are connected to a blast energy source ( 30 ) by means of a component ( 42 ) which forms part of the blasting system ( 10 ) and which is physically movable to a safe position, visually ascertainable by an operator, at which detonator ( 12 ) firing cannot take place if an unwanted or unsafe condition arises in the blasting system ( 10 ).

BACKGROUND OF THE INVENTION

This invention relates generally to a blasting system and more particularly is concerned with the safe management of power delivered to detonators or equipment in a radio frequency or remote wired blasting lead-in system.

A remote blasting system, for example a system which uses radio frequency to control and initiate a blast, normally employs an electronic or software system, with or without encryption techniques, to fire the blast. A blast energy source, which can be found in a downstream communication unit, is physically connected to detonators in the system which therefore relies only on logic and software security techniques to ensure that the blast is not initiated prematurely nor without upstream control.

A difficulty with this type of remote blasting system is that if a problem is encountered in the blasting area there is often uncertainty as to whether or not the blast energy source is connected to the detonators. This uncertainty means that the blast system cannot unequivocally be declared to be safe nor can it be said with impunity that personnel are free to enter the blast site.

A further risk which can exist is that, once a downstream control unit is connected to the detonators, an immediate or premature initiation of the system, during power up or connection of a detonator harness, can only be stopped by an electronic command signal. This carries with it the consequence that firmware, software or specific electronic failures can initiate an unplanned blast.

SUMMARY OF INVENTION

The invention is concerned with a blasting system which at least partly addressees the aforementioned problems and which provides for the safe management of power to detonators in the blasting system.

The invention provides a blasting system which includes at least one detonator, a blast energy source, a connection between the blast energy source and the at least one detonator, and control equipment for controlling initiation of the at least one detonator by causing energy from the blast energy source to be supplied to the at least one detonator, and wherein at least one component of the blasting system is physically movable from an operative position to a safe position, which is visible by an operator, at which blast energy from the energy source cannot be supplied to the at least one detonator.

The component may be selected from the blast energy source and a link in the connection.

The component may be moved, or be caused to move, in any appropriate way. The component may for example be movable by means of a biasing mechanism which is held in a first state when a first acceptable set of conditions pertains in the blasting system and which is released to a second state when an unacceptable condition arises in the blasting system. In the second state the component is in the aforementioned safe position.

This movement of the component to the safe position may be caused or initiated by at least one of the following:

-   a) after a predetermined period of time has elapsed from a given     starting time—the starting time may for example be a time at which     the component was moved from the safe position to the operative     position; -   b) after communication was established on the connection by means of     the control equipment followed by a malfunction; and -   c) if a malfunction of part or all of the control equipment occurs.

The control equipment may include an upstream control unit and a downstream control unit, the latter unit being closer to the detonators than the former unit and wherein the downstream unit is incapable of generating a blast command signal but can receive a blast command signal from the upstream control unit and transfer the blast command signal to the at least one detonator.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is further described by way of examples with reference to the accompanying drawings in which:

FIG. 1 is a block diagram representation of a blast system according to the invention;

FIG. 2 is a schematic representation of a downstream blast control unit included in the blast system of the invention;

FIG. 3 illustrates the construction of a mechanism for moving a link in the blast system between an operative position and a safe position; and

FIGS. 4 and 5 show different mechanisms which can interrupt a blasting process for safety reasons.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 of the accompanying drawings illustrates a blast system 10 according to the invention which includes a plurality of detonators 12 which are connected to a harness 14, a downstream blast control unit 16, an upstream blast control unit 18, a connection 20 between the upstream unit and the downstream unit, and additional or optional control equipment 22.

The detonators are installed in a defined blast pattern, in blast holes, as desired.

The connection 20 may be effected via a wired connection i.e. by means of a conductor 24, or wirelessly through the medium of a radio system 26 which includes two transmitting/receiving antennas respectively connected to the units 16 and 18.

FIG. 2 illustrates, enclosed in dotted outline, the construction of the downstream blast control unit 16 which is connected via the harness 14 to the detonators 12. On an incoming side the unit 16 is connected to a blast energy source 30. This can be a power source such as a battery, or a voltage step-up circuit with a voltage level which is capable of energising a detonator to set off a blast. As is noted hereinafter this source can be ejectable from an operative to a safe position. Alternatively a similar effect can be achieved by ejecting a connection, not shown, which connects the blast energy source to equipment which controls the application of energy from the blast energy source to the detonators, from an operative position to a safe position, upon the occurrence of an unsafe or potentially unsafe situation.

The unit 16 includes first and second timers 32 and 34 which control respective switches or links 32A and 34A, a voltage monitor 36 which has an audio output 38 and a visual output 40, a link 42 the physical construction of which is shown in further detail in FIG. 3, and a control circuit 44 which is responsive to a receiver and transmitter 46. The control unit and the receiver/transmitter may be duplicated, as is indicated in dotted outline in FIG. 2, for redundancy purposes.

The link 32A is independently operated by the timer 32 which is activated automatically upon start up of the downstream blast control unit 16. At start up the link 32A is closed and it is opened automatically after a predetermined period which is measured by the timer 32. This period is independently fixed and it is not dependent on any component of the system 10. The function of the timer 32 is to ensure that the system returns to a state of safety after the predetermined time period. The timer 32 may be electronic or mechanical but, preferably, the timer is not microprocessor-based i.e. it is not dependent on software or software routines.

The link 34A is also in the blast energy path between the blast energy source 30 and the detonators and, like the link 32A, it is activated upon start up of the downstream blast control unit 16. On start up the link is opened and it is closed after the timing period of the timer 34. The function of this link is to provide a safety or grace period before the system can be armed, during which personnel who armed the blast system are able to leave the blast site under safe conditions.

The monitor 36 monitors the voltage on the line downstream of the link 34A. Detection of a voltage on the line is indicative that the link 34A is closed and then, to ensure safe operation, the link 42 must not be closed. If a voltage is detected on the line then the audio and visual alarms 34 and 40 respectively are energised.

One embodiment of the link 42 is shown in FIG. 3. The link can take on a variety of forms (see FIGS. 4 and 5) but it should provide a visible indication, ascertainable from a safe distance, that it is in an open or closed state, as the case may be. Thus the link should include at least one component which physically moves, and the position of which is indicative of the state of the link.

The normal state of the link 42 is open and an active action is required to place the link in a closed state. The link is designed to be responsive to any undesired condition in the blast system, for example a power failure or malfunction in the control unit 44 or the timer 32. These events are given only by way of example for the link, as stated, could be responsive to any other condition or parameter which can be monitored.

The FIG. 3 embodiment of the link 42 includes a housing 50 with a close fitting cup-shaped plunger 52. Lower ends of the plunger include contacts 54 and 56 respectively which, when the plunger is inserted to a maximum extent into the housing, are brought into direct electrical contact with corresponding contacts 58 and 60 respectively fixed to an inner surface of the housing at a lower end thereof. Conductors 62 and 64 extend from the contacts 58 and 60 and, as shown in FIG. 2, go to the link 34A and a link 66 which is controlled by the control unit 44.

A spring or any equivalent biasing mechanism 70 is inside the housing and normally urges the plunger 52 away to extend out of the housing. A conductor 72 is embedded in the plunger and extends between the contacts 54 and 56. Two metal slugs 74 and 76 are fixed to an inner surface of the plunger and oppose solenoids 78 and 80 mounted to a base 82 of the plunger. If the solenoids are energised and the plunger is pushed inwardly then the solenoids exert sufficient attractive forces which act on the metal slugs 74 and 76, to keep the plunger in a retracted position. If the power supply to either solenoid is interrupted then the attractive force is at least halved or, if both solenoids are de-energised, the attractive force is reduced to zero. In each case the biasing force of the spring 70 is then such that, automatically, the plunger is pushed out of the housing 50 to a position which is clearly visible and which indicates to an observer that the electric connection between the conductors 62 and 64 is broken.

The downstream blast control unit is under the control of the control unit 44. The control unit 44 will only close the link 66 if a valid command is received from the upstream blast control unit 18 which is under operator control. Alternatively or additionally a valid signal can be generated by and transmitted from the additional control unit 22.

As is indicated in FIG. 1 communication from the upstream unit to the downstream unit can be established via a physical hard wire connection 24, or wirelessly over the antenna system 26. In the latter case the antenna which is shown in FIG. 1 as being connected to the downstream blast control unit 16 is connected to the receiver/transmitter unit 46 of FIG. 2.

The control unit can be responsive to a command instruction from the upstream unit 18 to interrupt the power supply to one or both the solenoids 78 and 80 thereby to cause the link 42 to be activated whereupon the plunger 52 is substantially ejected from the housing 54. A similar process takes place if the control unit establishes that the integrity of any component or module in the blast system has been compromised.

The redundancy circuits, marked 44A and 46A, are essentially duplicates of the modules 44 and 46 respectively and function in the same way to ensure that backup is automatically provided upon failure of either module. One or both of the circuits can be coupled to the link 42 and cause activation of the link, thereby placing the system in a state of safety, if a circuit malfunction occurs.

The transceiver 46 does not take part in any interlocking or blasting decisions. Its function is to channel the data stream between the upstream and downstream control units.

When a blast is to be established an operator starts up the blast control unit 16 whereupon the timer 32 commences its timing cycle and closes the link 32A. Communication is then established between the upstream and downstream control units as required. The link 42 is closed by the operator pushing on the plunger 52 so that it goes into the housing and bridges the contacts 58 and 60. The monitor 36 constantly monitors the line 62 and if a voltage is detected on the line the operator is alerted and can take appropriate action. If any malfunction should occur the link 42 is automatically opened in the manner described.

If the timing period of the timer 32 is exceeded, for whatever reason, without the blasting system being fully armed, then the link 32A automatically opens. When this occurs the link 42 is also opened to provide a visual indication that the system has been returned to a safe state.

Once the blasting system has been established and the blasting system is to be armed, the link 34A is opened for a predetermined time period, set by the timer 34, during which all personnel should leave the blast site. On expiry of the time period the link 34A is closed and the detonators can be armed and thereafter fired with a blast command signal generated by the control equipment. Thus the timer 34 provides a grace period during which personnel can leave the blast site with safety before the electronic control system takes control of the detonators.

If a malfunction occurs during the arm and blasting stages then the physical link 42 is automatically opened and is moved to a position, which is visible from a distance, at which the conductor 62 is electrically disconnected from the conductor 64. Thus personnel know that they can re-enter the blast site with safety.

FIG. 4 shows a component 42A which can be used in place of the link 42 shown in FIG. 3. The component includes opposed solenoids 84 and 86 each of which acts on a respective latch 88 and 90, mounted for pivotal movement about a respective axis 92 and 94. Structure 96 which, according to requirement, carries a visible blast energy source (eg. a battery), blast energy converter or a connector, designated 98, is held in an operative position (as shown) by the latches 88 and 90. However, if a command instruction is received from the upstream unit 18 or if a malfunction is detected then the power supply to one or both solenoids is interrupted. A spring 100 on a plunger 102 of a de-energised solenoid then rotates the respective latch in the direction of an arrow 104 or 106, as the case may be. A spring-loaded member 108 then forces the structure 96 upwardly to provide a visible indication of the circuit interruption.

One or more electrical contacts in the member 108 or associated with the structure 96 are simultaneously broken so that the system is thereby automatically placed in a state of safety.

FIG. 5 shows another possible form of the link 42. A component 42B includes structure 96B, which can carry a blast energy source or converter, or a connector link, and which is mounted for pivotal movement about an axis 110. A solenoid 84B acts on a latch 88B which moves about a pivot 92B and which can retain the structure in an operative position, as shown.

When the structure is moved to the operative position a coil spring, not shown, centred on the axis 110, is biased. If for any reason, e.g. a malfunction occurring in the blasting circuit, the solenoid is de-energised, the spring causes the structure to pivot upwardly, about the axis 110, in the direction of an arrow 112. A cam formation 114 on the structure then acts on a spring-loaded plunger 116 and breaks an electrical connection or connections in the blasting circuit which is thereby rendered safe.

Again, a visible indication is given to personnel of the change of state, and the blast site can be re-entered with safety. 

1-12. (canceled)
 13. A blasting system which includes at least one detonator, a blast energy source, a connection between the blast energy source and the at least one detonator, and control equipment for controlling initiation of the at least one detonator by causing energy from the blast energy source to be supplied to the at least one detonator, a mechanism which is held in a first state when a first acceptable set of conditions pertains in the blasting system and which is automatically released to a second state when an unacceptable condition arises in the blasting system, and wherein at least one component of the blasting system is physically movable by the mechanism from an operative position to a safe position, which is visible by an operator, at which blast energy from the energy source cannot be supplied to the at least one detonator, when the mechanism is released to the second state.
 14. A blasting system according to claim 13 wherein the component is selected from the blast energy source and a link in the connection.
 15. A blasting system according to claim 14 wherein the mechanism is biased to the second state.
 16. A blasting system according to claim 13 wherein the mechanism is biased to the second state.
 17. A blasting system according to any one of claims 13 to 16 wherein movement of the component to the safe position is due to at least one of the following: (a) the elapsing of a predetermined period of time from a given starting time; (b) the occurrence of a malfunction in the blasting system after communication was established on the connection by means of the control equipment; and (c) the occurrence of a malfunction in part or all of the control equipment.
 18. A blasting system according to any claim 17 wherein the control equipment includes an upstream control unit and a downstream control unit which is closer to the at least one detonator than the upstream control unit and wherein the downstream unit is incapable of generating a blast command signal but can receive a blast command signal from the upstream control unit and transfer the blast command signal to the at least one detonator.
 19. A blasting system according to any one of claims 13 to 16 wherein the control equipment includes an upstream control unit and a downstream control unit which is closer to the at least one detonator than the upstream control unit and wherein the downstream unit is incapable of generating a blast command signal but can receive a blast command signal from the upstream control unit and transfer the blast command signal to the at least one detonator.
 20. A blasting system in which detonators are connected to a blast energy source by means of a component which forms part of the blasting system and which is automatically physically movable to a safe position, visually ascertainable by an operator, at which detonator firing cannot take place if an unwanted or unsafe condition arises in the blasting system.
 21. A method of operating a blasting system which includes the steps of establishing a connection between a blast energy source and at least one detonator, and of automatically physically moving a component of the blasting system from an operative position to a safe position, which is visible by an operator, at which blast energy from the energy source cannot be supplied to the at least one detonator when an unacceptable or unsafe condition arises in the blasting system.
 22. A method according to claim 21 wherein the component is selected from the blast energy source and a link in the connection.
 23. A method according to claim 21 or 22 wherein movement of the component to the safe position is caused or initiated by at least one of the following: the elapsing of a predetermined period of time from a given starting time; the occurrence of a malfunction after communication was established on the connection; and the occurrence of a malfunction in control equipment which is used to generate a blast command signal. 